Like previous posts, it's an airspace issue, but it is the 'norm' for approach into either end at LTN.
If the odd FIS request gets in the way, I'd personally step on them to get an established call in - you'll find ATC won't bollock you for this, most of them see it happening anyway and will ignore the GA stuff to ensure you're cleared for the glide.
If not you can always slow right down and ask for a lower altitude to intercept (not ideal, but certainly an option).